A continuous line of Friend virus transformed mouse leukemic cells has been established which can be induced to differentiate along the erythropoietic pathway by simply adding dimethylsulfoxide (DMSO) to the culture medium. Late in the development process nearly 30% of the newly synthesized soluble cytoplasmic protein is adult alpha and beta globin chains. Our ultimate goal is to determine the molecular mechanisms controlling the development process. We will first attempt to obtain a more thorough description of the developmental program by analyzing cultures at different stages of development for differences in activities of select enzymes and patterns of protein synthesis. We will also investigate possible changes in membrane proteins and surface antigens. Special emphasis will be placed on determining the role of the Friend virus in the development process. We will attempt a biological and biochemical characterization of the virus produced in control and DMSO induced cultures. The effects of various potential inhibitors and promotors of virus growth on the development process will be analyzed. Finally, we will attempt to isolate cellular variants which are either noninducible by DMSO or defective in virus production in order to determine if there is a correlation between the erythropoietic potential of a cell line and the nature or quantity of virus it produces.